This invention relates to motion picture film projectors of the type used in motion picture theaters. In a typical installation, the film projector is mounted on a console and carries a lens turret and one or more motors for changing lenses and film aperture. The console which carries the projector includes the projection lamp, reflector, heat filter, lamp power supply, optical system and control panel.
Various aperture shapes are used in present day film. In one arrangement, two apertures are used; typically one shape is nearly square and is sometimes referred to as the Cinemascope or "scope" aperture. The other is rectangular with a side-to-side ratio of about 1.85 to 1, and sometimes is referred to as the "flat" aperture. The two types of film often are spliced together for continuous showing and cues are incorporated at the splices to provide control signals to the lens change and aperture change motors so that the projector is properly configured for the particular film being shown.
The beam of light from the high intensity lamp is circular and therefore some lamp energy is blocked at each of the apertures. Reflectors providing elliptical beams have been tried but have not been satisfactory. Since the projector apertures have different length to width ratios, it is the practice to focus the beam to a size which is a compromise between the sizes preferred for each of the two apertures. Alternatively, the projector operator can manually change the focus. However, changing focus is not a practical solution to the problem because an operator is not present in the projection booth at all times in today's theatres.
It is an object of the present invention to provide a new and improved lamp mounting arrangement which will provide for automatically changing the lamp position and thereby the lamp focus and beam shape to achieve maximum efficiency for each of the aperture shapes. A further object is to provide such a system which will utilize the control signals from the film cues for automatically changing the lamp position as the type of film being projected changes.
These and other objects, advantages, features and results will more fully appear in the course of the following description.